Explosive embedment rock anchor



March 11, 1969 O PANNELL 3,431,880

EXPLOSIVE EMBEDMENT ROCK ANCHOR Filed Dec. 18, 1967 I INVENTOR or/s R. PANNELL AGE/VT BY I ORNEY United States Patent 3,431,880 EXPLOSIVE EMBEDMENT ROCK ANCHOR Otis R. Pannell, Alexandria, Va., assignor to the United States of America as represented by the Secretary of the Navy Filed Dec. 18, 1967, Ser. No. 691,533

US. Cl. 114-206 3 Claims Int. Cl. B63!) 21/28 ABSTRACT OF THE DISCLOSURE An explosive rock embedment anchor assembly having a shaped charge explosive for producing a hole in a hard ocean floor, and a projectile gun for subsequent embedment of a projectile anchor in the hole.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Background of the invention This invention relates to rock embedment anchors and more particularly to explosive rock embedment anchors having a shaped explosive charge to produce a tapered hole in the rock bottom for subsequent embedment of a projectile anchor by propelling it into the hole with an explosive charge gun.

Heretofore, there have been no satisfactory means of anchoring ships, barges, work platforms, underwater pipelines and other type vessels and equipment to a solid rock or coral ocean floor. Particularly when the ocean floor is composed of smooth rock, anchoring to these hottoms by the use of dead weight or the installation of grouted piles is sometimes attempted, but the installation of these ancharoges is expensive and time consuming. The use of the common fluke-type anchor is undesirable in that no positive and secure anchorage point is possible. In cases where the rock bottom is jagged, the common fluke-type anchor may be used but the procedure requires several dragging tries before the anchor will catch in a crack or crevice near the desired anchorage position.

Many attempts have been made to develop rock embedment anchors which penetrate a hard rock ocean floor, :but these have not been entirely satisfactory. The prior art includes many designs, but these usually take the form of a projectile anchor and propellent gun for driving the projectile directly into the unprepared rock ocean floor. Penetration is often very slight and therefore secure anchorage is not possible or inadequate.

Summary This invention provides an explosive rock embedment anchor having a shaped charge for producing a hole which will provide adequately secure anchorages in hard ocean floors and therefore solves the problem of the normal or common fluke-type anchors and circumvents the disadvantages of the prior art rock embedment anchors. This explosive embedment rock anchor lends itself readily to usage in anchoring underwater systems and platforms and for use in salvage operations of beached equipment.

This novel explosive rock embedment anchor of the invention comprises four primary parts: (1) A shaped charge for producing a large tapered hole in the rock ocean floor; (2) A housing for the shaped charge which directs the explosive force of the shaped charge in the desired direction; (3) A projectile anchor having a star shaped head for insertion into the hole produced by the shaped charge; and (4) A propellent gun for explosively driving the projectile into the hole produced by the shaped charge. The ancilliary parts include the frame for holding the shaped charge housing and the projectile gun in the proper positions, a wire rope riser for attachment to the object to be securely anchored, and a tripodal base for supporting the assembly in an essentially, vertical position on the bottom. The riser may be attached before embedment in the rock bottom or it may be subsequently attached by divers after embedment. In the case of use of this rock embedment anchor in a rock bottom overlayed with mud, water jet producing means may be attached to the frame to dislodge the mud so as to allow the anchor frame to sink to a position closer to the rock bottom.

Accordingly, it is the principal object of this invention to provide an economical and rapid means of providing secure anchorages in ocean floors composed of solid rock or coral.

Another object of this invention is to provide an explosive rock embedment anchor which is light weight and readily stowed.

Other objects and features of the invention will be come apparent to those skilled in the art upon reference to the accompanying specification, claims, and drawing in which:

Brief description of the drawing The figure is a cross-sectional elevation view of the explosive rock embedment anchor assembly according to this invention.

Description 0 the preferred embodiment Referring now to the figure, there is shown an explosive rock embedment anchor assembly 10 comprising four upwardly splayed legs 12 attached at their bottom to a. shaped charge housing 14 in the form of an open-ended tube, and at their top ends to a drag cup 16 which is rigidly afiixed to the projectile gun barrel 19. The drag cup 16 functions to reduce recoil by providing large water resistance to movements of the assembly when the explosive charges are fired. The gun 18 is military standard equipment. Rigidly attached to the drag cup 16 are three downwardly splayed legs 13 which contact the ocean floor to provide a tripodal support for the assembly 10. A projectile anchor 20 is frictionally engaged within the barrel 19 of the gun 18, leaving exposed a tapered projectile head 22 which is star shaped in transverse cross section.

A seal is provided for the shaped charge housing 14 in the form of a plug 24 of frangible material such as hard Wood. The plug 24 has an external diameter greater than the internal diameter of the housing 14 and is driven into the upper end of the housing to provide a watertight seal therefor. The point of the projectile head 22 is drawn against top surface of the frangible plug 24 by the legs 12 and thereby retains both the projectile 20 within the barrel 19 of the gun as well as plug 24 within the shaped charge housing 14.

The shaped charge 26 has the external configuration of a cylinder having a diameter less than the internal diameter of its housing 14 so that the shaped charge may readily fit within the housing. As shown in the figure, the shaped charge 26 has a conical void 27 within the mass of the explosive to obtain the shaped charge effect upon explosion. The bottom of the housing 14 is sealed against the ingress of water by a plastic plug or cap 28.

At the top end of the projectile head 22, a wire rope riser 30 for use in attachment to the object to be anchored is shown installed through a hole in the projectile anchor 20.

3 Description of the operation The installation of the explosive rock embedment anchor of this invention is commenced by lowering the assembled unit in a vertical position until the bottom of the shaped charge housing 14, as well as the three legs 13, contact the ocean floor. The shaped charge 26 is then detonated remotely by means of electrical conductors (not shown) connected between the anchor assembly and a suitable location of electrical power, such as, on the vessel to be anchored. After detonation of the shaped charge, a short time is allowed to elapse for the explosive gases to dissipate and for the particulate debris to clear the hole produced by the charge in the ocean floor. The projectile gun 18 is then fired by means of electrical conductors (not shown) connecting the gun to a suitable remote energizing source. The propellent charge causes the head 22 of the projectile anchor 20 to embed in the sides of the hole in the rock produced by the shaped charge. The projectile head 22 is made high alloy steel, the cross-section of which is star-shaped and in elevation tapers from a point to a larger dimension at the top of the head 22. The sharp tapered edges of the star-shaped head 22 therefore wedge and embed themselves in the side of the hole thereby becoming tight and providing an adequately secure anchorage. Anchor lines or cables may be attached to the wire rope riser 30 either before or after embedment of the head 22.

It is to be understood that the invention is not limited to the exact details of the construction shown and described, for obvious modifications will occur to persons skilled in the art. As an example, and not by way of limitation, the drag cup 16 may be dispensed with or reduced in size by providing for the gun 18, a recoilless type of suitable known construction.

What is claimed is:

1. An explosive embedment anchor assembly compnsmg:

a projectile gun;

a projectile, in said gun, having a tapered head of star-shaped cross section for embedment in the ocean floor;

a shaped charge housing of cylindrical configuration, having an open end, said housing being coaxially subjacent said projectile and adapted to contact a hard bottom of the ocean floor;

frangible plug means sealing the open end of said shaped charge housing;

a shaped charge explosive within said shaped charge housing capable of producing a hole in the ocean floor; and

a plurality of legs for rigidly connecting said projectile gun and said shaped charge housing to form an integral assembly whereby the point of said projectile is maintained in abutment With said frangible plug means.

2. The explosive embedment anchor assembly of claim 1 wherein said projectile gun further comprises a drag cup for counteracting recoil upon detonation of said shaped charge and said projectile gun.

3. The explosive embedment anchor assembly of claim 2 further comprising a tripod attached to the assembly for supporting the assembly on the ocean floor in essentially a vertical position.

References Cited UNITED STATES PATENTS 3,154,042 10/1964 Thomason et al. 114-206 3,315,629 4/1967 Standridge et a1 114206 TRYGVE M. BLlX, Primary Examiner. 

